Death wobble

B

billbender46@gmail.co

New member
I have been chasing a “death wobble” on my ‘31 Roadster.

Today we used a “toe-in” measurement tool to check the “toe-in”. We actually made an error in reading the device and ended up setting my car at about 3/32” toe-out. Took it for a drive and it was smooth (no wobble).

While we had the borrowed tool we decided to check my buddy’s ‘31 Sedan. In doing so, we realized that we read the tool wrong. We decided to correct the mistake on my car, and the wobble was back.

The only unique piece of this puzzle is that I have radial tires on my car. Has anyone else had a similar experience with having to set the front end at about 1/8” toe-out to avoid severe wobble?
 
If you experience wobble after setting the toe-in to spec, then you likely have other worn steering components.
You are compensating for worn components by setting toe-out, which increases the force on king pins and tie-rod ends. It's that increased force that is taking the play out of your components. You are also scrubbing your tires.
Also don't overlook the engine front to alignment and radius ball which would affect caster.
 
Something is definitely wrong. The 'death wobble' is usually from looseness somewhere from the steering box/adjustment out to the wheel bearings and anything in between.

You certainly don't want the tires toe-d out. They should be 1/32-1/16" in.
 
Try and tighten the king pin wedge bolts. Also ...is your front spring flat and 90 years old?
This has a effect on the front in geometry.
 
Patrick L. said:
Something is definitely wrong. The 'death wobble' is usually from looseness somewhere from the steering box/adjustment out to the wheel bearings and anything in between.
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as so often I agree absolutely with Patrick! The shimmy/wobble can be from any component in the steering inc radius ball, slack pitman arm, kingpins, slack drag link or track rod ball spring tension ,king pins, bearings, steering geometry etc etc etc ... it's often a case of just tightening something up:), at other times a steering rebuild:(
 
the other thing to consider is the size of your tires. if you do have worn parts, they can be accentuated by larger tire size, which many choose, for a softer ride.
 
Shimmy!

90 plus year old car. When was the last time your front end was rebuilt or at least completely inspected?

Front end, brakes, shocks, and springs! They “must” be right.

Adjust a little here, fix a little there, and than wonder why things never seem to be correct.

Sorry for my soap box. After 60 years, I have learned there is only one way to correct a problem. Inspect completely, rebuild completely, or replace completely. Do it right once. Than it’s done and you can move on to the next issue.

Good luck.
 
A Truck inspection method the highway patrol uses is effective.Have someone rock the steering wheel back and forth with the car on the ground..visually inspect from pitman arm to wishbone ball every point of movement. If you see play, fix it. Rest your hand on the tire at one point, if you feel a ‘click’ check wheel bearings too
 
jack backer said:
Have someone rock the steering wheel back and forth with the car on the ground..visually inspect from pitman arm to wishbone ball every point of movement. If you see play, fix it. Rest your hand on the tire at one point, if you feel a ‘click’ check wheel bearings too
Click to expand...

Ditto
 
jack backer said:
A Truck inspection method the highway patrol uses is effective.Have someone rock the steering wheel back and forth with the car on the ground..visually inspect from pitman arm to wishbone ball every point of movement. If you see play, fix it. Rest your hand on the tire at one point, if you feel a ‘click’ check wheel bearings too
Click to expand...

That is the way to do it. With the weight on the tires, have someone rock the steering wheel back and forth while you watch for any movement, including play in the steering box gears. I was a phone company mechanic and we had big trucks subject to DOT 90-days inspections. When we knew the CHP was coming, we checked all that stuff ahead of time. They were checked like that on every service. Any vehicle with front-end problems that was how we started off searching for the problem. If there was no play, we put it up in the air and spun the tires to make sure they were not separating. Then we pulled them off and balanced them on a computerized wheel balancer. If they took an unusual amount of weights, we got rid of the tires. We tried rotating the tires. New shocks, We checked the front-end alignment, they usually needed a little toe-in adjustment. Caster and camber would change daily depending on much weight they carried. Somedays they had a lot of cutup poles in the back.

We had F350s aerial boom trucks with death wobbles issues from the day they were new. They were loaded to the maximum GVW and if everything was not perfect, one bump in the road and they shook violently until you brought them to a stop. The shocks had to be new, the tires balanced and perfectly round, alignment correct and absolutely no play in anything, especially the panard bar bushings. A couple years later Ford installed steering stabilizer shocks and that didn't help. We had already tried that on the earlier ones. Some designs can all kinds of issues and never have speed wobbles and some are real sensitive to anything not being perfect. Those F350s were straight axles too.

Anytime you change factory settings to fix a problem you're just masking the real issue and probably creating a new problem at the same time. The toe-in is there is to make the car drives straight down the road. The front of the tires are slightly angled inward, together they both aim at a single point ahead of the vehicle which helps it go straight. By changing the toe-in to toe-out, it will cause tire wear but it will also cause the vehicle wander around.
 
Ever had one of those super duty tires come apart on ya? Had one on a Coates machine, flat repair (worked a small fleet,did everything) took it off aired it up without using a cage…sounded like zipper on a ladies dress, after the explosion we found they were the wires in the steel belt snapping… I use a long lead on the tire filler, the only thing that happened to me was filling my shorts with doo doo..
 
One fella failed to use the cage, ring let go and struck him under the chin. Shop was of course closed for the funeral.
 
What I find on Restored cars is only minimum front end maintenance is done over the years,Because
It's Restored.....This means the last owner didn't drive the car,the car sat for years,so it's still new.
This may go on for 10-20 years. The real story is someone did drive it. Every A and T I pick up,something is wrong with every front end. King pins 90% of the time.
 
I’ve seen a few pretty cars that wouldn’t make it around the block.Often owned by folks who pick your car apart and love to tell you what’s wrong with yours. The mentality has been developed over the years by clubs and judging.. the original intent of restoration was to bring people together, to learn..now it’s used as a cudgel, to set a pecking order.
 
Wick said:
What I find on Restored cars is only minimum front end maintenance is done over the years,Because
It's Restored.....This means the last owner didn't drive the car,the car sat for years,so it's still new.
This may go on for 10-20 years. The real story is someone did drive it. Every A and T I pick up,something is wrong with every front end. King pins 90% of the time.
Click to expand...

Right on the mark.

It’s not how it looks it’s all about how it drives. You can put makeup on a pig. It’s still a pig.

I spent most of my time on the running gear. The body is easy.
 
I always do my cars with it being a driver in mind. This is the primary function of a car! Simply put, I hate Death Wobble and have spent an inordinate amount of time getting rid of it. Usually something is loose. I've found that the parts seem to stay in place until a bump or a turn or something knocks them out of place. Then things go haywire and we find out why they call it "death wobble". And it's not restricted to Model A s. Cars of the 1950s would have it when the idler arms were worn out. So to diagnose it, with the car parked, do the wheel bearing shake, top to bottom! If they're ok (Tight ) go to side to side. If there's motion, see what's moving with the wheel. Then check the steering balls. Steering balls flatten out to where it's hard to believe they were once spherical, but they were! The balls should be 1.000 -.020 O.A. (Over all) Look for them on the left side of the car. First one is on the Pitman arm and there's more as you progress down through the steering linkage. Assuming that's ok, jack the right wheel up and check the wheel shake for a bad kingpin (Steering bolt) Hand on the top and the bottom of the wheel. Watch the spindle. If it moves with the wheel it's the kingpin. if it moves but the spindle is rigid to the axle, it's the bearing. Another thing to look for, are the spring eyes centered on the the spring perch bolt? or is the spring laying (touching ) the axle? Replace the spring bushings if they are. There are other cause of death wobble (Wheel balancing, alignment , etc) but these are the most common.
Terry
 
I always focus on toe-in, bearings, kingpins, steering balls, tie rod ends, spring and spring eyes, and radius ball first. The car should want to drive straight without wobble regardless of steering box, pitman, drag link play. Those items are NOT the cause of wobble. In fact, you should be able to disconnect the drag link entirely and the car should want to go straight (yeah... don't try this). Understanding a little about steering geometry helps to troubleshoot the problems.
 
While steering component wear will make a feedback situation worse, it is generally not the major cause of it. Automobile tires can be fabricated improperly during the wrapping or winding process of the rubber & reinforcing belt or ply to form the carcasses. The plys and belts can also separate or delaminate and this will cause the tire to wobble. A bad tire can usually be detected by removing the wheel assembly from the car and rolling it on a flat level surface. If it rolls true then it is likely in good condition for the most part or at least at slow speeds. It's hard to tell though on some tires. They may not start to wobble until they reach a certain road speed or temperature if they are just beginning to delaminate the carcass. Feel of or take the temperature of tires after driving the car down the road for a good bit. A tire that is unusually hot when compared to the others is a dead giveaway that it's going south.

Keep a close eye on tire pressures for your cars. If you hit some big pot holes or run over some big road debris, it can damage the carcass. Monitor any tire that is suspect for a while just to make sure it is roadworthy. We take out tires for granted sometimes and that can be problematic.
 
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rotorwrench said:
While steering component wear will make s feedback situation worse, it is generally not the major cause of it. Automobile tires can be fabricated improperly during the wrapping or winding process of the rubber & reinforcing belt or ply to form the carcasses. The plys and belts can also separate or delaminate and this will cause the tire to wobble. A bad tire can usually be detected by removing the wheel assembly from the car and rolling it on a flat level surface. If it rolls true then it is likely in good condition for the most part or at least at slow speeds. It's hard to tell though on some tires. They may not start to wobble until they reach a certain road speed or temperature if they are just beginning to delaminate the carcass. Feel of or take the temperature of tires after driving the car down the road for a good bit. A tire that is unusually hot when compared to the others is a dead giveaway that it's going south.

Keep a close eye on tire pressures for your cars. If you hit some big pot holes or run over some big road debris, it can damage the carcass. Monitor any tire that is suspect for a while just to make sure it is roadworthy. We take out tires for granted sometimes and that can be problematic.
Click to expand...

Honestly, I have four model A s, two 30, coupes, a 29 blind back. and the 30 town sedan and I've had problems with death wobble with all except the 30. Invariably it has been a mechanical problem. Undoutably, bad tires can cause it, but I'd check the mechanicals first. Tom W. (RIP) was a proponent of poor alignment being the cause. This too, was never the cause in my cars, unless you think of the worn parts as the cause of the bad alignment, which it could very easily be. The cause (s) in my coupe (multiple) were a bad kingpin and the spring bushings being worn out. I repaired the kingpin and that helped, but didn't repair it all. I had to chase it down further . In my other coupe, it turned out to be the steering box needed rebuilding. I'm about to start on the blind back. But I found the RH wheel bearing was loose , I tightened it but haven'had the car on the road since, so I can't tell if it just needed tightening or more. I sincerely hope it's not the tires, I'd rather not buy a set of tires right now.
Terry
 
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